I feel your pain. It seems to me that reporting once per offensive message would be justified. Reporting 90x would put you into the ranks of an abuser; no better than the other guy. Is that what you really want?

Why not set up a better (if you have one) CAPTCHA system so you don't have to worry about auto submissions...which I'm guessing that's what it is...since I'm under the impression that people should not have the time to sit there and send 90 emails to 1 person...